Spherical metal particles or pellets, generally referred to as shot, find applications across a number of industries as abrasive media and are widely used as projectiles in shotshells for sporting purposes. Industrial shot is useful as an abrasive for etching a textured surface onto metal to enhance bonding with various coatings, or as a blast cleaning medium to remove surface contamination from metal products. Metal shot is useful in peening processes to impart compressive strength to torque-bearing metal parts such as jet engine turbine blades. For hunting and sporting use, shot pellets for shotshells can assume a range of sizes, compositions, and densities as the particular application dictates.
Conventional methods for producing of metal spheres include metering the molten metal into uniform portions that are dropped into water and cooled, while surface tension brings the molten sample into spherical form. Other methods impinge a jet of water or other fluid onto a stream of molten metal, which atomizes the molten metal to form metal spheres. While such methods may be suitable for producing high volumes of particles of nearly uniform size, they are not amenable to producing anything other than spherical or near-spherical particles.
Recently, non-spherical metal particles or shot have found utility in particular shotshell applications. For example, shot pellets having a smoothed hexahedral shape, that is, a cube with smooth or rounded edges and corners, show promise for improved hunting loads. The cubic structure of the pellets is more space-filling and packs more efficiently than spherical shot, thereby providing a greater mass of shot in the same unit volume as compared to spherical shot. This feature may be particularly useful for hunting loads where ballistic steel and various high density alloys are supplanting lead shot, as lead becomes more strictly regulated. One example of flattened spherical shot is illustrated in U.S. Pat. No. 3,952,659.
Therefore, methods are needed that can produce non-spherical metal particles, including metal cubes with rounded edges, efficiently and in high volume. What are also needed are methods that can provide non-spherical metal particles, which are amenable to mass production of metal cubes and are relatively economical.